The District of Columbia Water and Sewer Authority (DC Water) has initiated tunnelling for the Potomac River Tunnel Project, marking the start of one of the final phases of its ongoing Clean Rivers Programme.
At a ceremony in West Potomac Park in Washington, D.C, Mayor Muriel Bowser conducted a formal blessing of the tunnel boring machine (TBM), Mary, using DC tap water.
Discover B2B Marketing That Performs
Combine business intelligence and editorial excellence to reach engaged professionals across 36 leading media platforms.
Mary will excavate the northern leg of the planned 5.5-mile long Potomac River Tunnel.
The tunnel is expected to divert close to one billion gallons of combined sewage and stormwater each year during average rainfall conditions.
A second machine, Emily, is scheduled to arrive from Germany later in the year to construct the southern segment.
Together, the two machines are central to a project intended to substantially reduce sewer overflows into the Potomac River.
US Tariffs are shifting - will you react or anticipate?
Don’t let policy changes catch you off guard. Stay proactive with real-time data and expert analysis.
By GlobalDataDC Water CEO and general manager David L. Gadis said: “Today we celebrate not just a machine, but a movement.
“The Clean Rivers Program has been a game-changer for our city. We’ve watched the Anacostia River come back to life, and now, with Mary leading the way, we’re turning our focus to the Potomac. This tunnel is one of the final pieces of a legacy that will leave our rivers cleaner, our communities healthier, and our future brighter.”
The Potomac River Tunnel is designed to lower combined sewer overflow events from 74 to just four annually and cut related discharge volume by 93% when completed in 2030.
The infrastructure includes a deep tunnel, diversion facilities, drop shafts such as the 100-foot-deep shaft at the launch site, and support structures. These will collect wastewater from eight existing outfalls along the river, directing flows to the Blue Plains Advanced Wastewater Treatment Plant.
Design activities for the Potomac River Tunnel began in 2019.
Construction mobilisation at West Potomac Park started in 2024. Upon completion of the tunnelling project, DC Water forecasts significant improvements in both the volume and frequency of untreated overflows entering the Potomac River.
